The invention relates generally to welding power supplies, and, more particularly, to a digital controller for a switched mode welding power supply.
Many types of welding power supplies capable of providing a welding power output from an alternating current (AC) or a direct current (DC) source of power have been developed. One such welding power supply is a switched-mode power supply, which utilizes power semiconductor switches to chop DC power from a source and convert the chopped power to a voltage and/or current suitable for welding. Switched-mode power supplies such as inverter type power supplies and chopper type power supplies have been developed to meet the needs of various welding processes and applications.
The chopper and inverter type power welding power supplies are typically controlled by similar control methods and/or circuits. One method of controlling such power supplies is with a pulse width modulation (PWM) control. A PWM control provides for regulation and control of the output current and/or voltage of the welding power supply by varying the duty cycle (i.e., the ON/OFF ratio) of power semiconductor switches located in the power supply circuitry. Traditional inverter or chopper welding power supplies include a closed loop current control loop, such that the power supply may be operated as a controlled current source for certain arc welding load conditions. As such, traditional inverter or chopper welding power supplies include an analog controller, which controls the minimum and maximum current levels output from the power source, the rates of change of current between various levels, the generation of desired current waveforms, and so forth. Unfortunately, analog controllers are often associated with drawbacks, such as the inability to adequately handle the dynamic requirements of a switched-mode welding power supply. For example, analog controllers often fall short of responding quickly enough to quickly occurring events in a welding arc, may happen with time intervals of less than 1 msec. Accordingly, there exists a need for improved control systems and methods for switched-mode welding power supplies.